[ We would like to hear feedback on this. We are planning to revise and
submit a new version ASAP, so please voice opinions on this within the next
few days, by Monday, June 24th. ]
Background:
Today, the ALTO protocol as a 'version tag' to indicate which version of a
network map is used by a particular cost map.
In a particularly simple case, a single ALTO server is served by a single
hostname (or IP address, whatever), and it exposes a single network map and
one or more cost maps. There is no ambiguity here - a client automatically
knows that any version tag refers to the single network map that is hosted
by the server.
There are two alternate scenarios where ambiguities arrive:
(Scenario 1) An IRD hosted by alto.isp1.example.com refers cost maps
provided by some third-party, say alto.third-party.example.com. In this
scenario, do version tags exposed by
alto.third-party.example.comcorrespond to the network map provided by
alto.isp1.example.com?
(Scenario 2) A single ALTO server (single hostname) wishes to provide two
different network maps (say, different levels of aggregation) and wants to
provide cost maps for each of them. Currently, the version tag
accompanying a cost map is not sufficient for a client to determine which
network map a particular cost map is based on.
Proposal:
To resolve these problems, we'd like to propose a simple change to the
version tag accompanying the cost map - it would now include the URI to the
network map in addition to an opaque ID.
OLD (what we have now):
{
"meta" : {},
"data" : {
"cost-type" : {"cost-mode" : "numerical",
"cost-metric": "routingcost"},
"map-vtag" : "1266506139",
"map" : {
"PID1": { "PID1": 1, "PID2": 5, "PID3": 10 },
"PID2": { "PID1": 5, "PID2": 1, "PID3": 15 },
"PID3": { "PID1": 20, "PID2": 15 }
}
}
}
NEW PROPOSAL:
{
"meta" : {},
"data" : {
"cost-type" : {"cost-mode" : "numerical",
"cost-metric": "routingcost"},
"network-map" : {
"uri": "http://alto.example.com/networkmap1";
"vtag": "1266506139"
}
"map" : {
"PID1": { "PID1": 1, "PID2": 5, "PID3": 10 },
"PID2": { "PID1": 5, "PID2": 1, "PID3": 15 },
"PID3": { "PID1": 20, "PID2": 15 }
}
}
}
Compared to the current approach we have in draft -16 (which is for a
version tag to be consistent within resources served by the same hostname),
this has the following advantages:
- It provides a more flexible solution to Scenario 1
- It allows us to handle Scenario 2
An possible addition to this approach would be explicitly declare the
dependency between the cost map and the network map in the IRD.
Feedback would be great. The editors believe this would be a strong
improvement to the draft.
Thanks,
Rich
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